1. Field of the Invention
The present invention relates to a torque wrench device which can be combined with various types of commercially available wrenches such as a spanner wrench, ring spanner, ratchet wrench, hexagonal wrench key, wheel wrench and so forth, so as to enable the wrench to tighten an object with a required level of torque. The invention also is concerned with a torque wrench device which enables setting of the tightening torque without requiring adjustment of compression load of a compression coiled spring incorporated therein.
2. Description of the Related Art
A typical conventional torque wrench device designed for tightening a bolt or the like with a predetermined level of torque is shown in FIG. 1.
The torque wrench device has a tubular torque wrench handle 1. A head 2 is pivotally secured to an end of the handle 1 by means of a head pin 3. The handle 1 accommodates a thruster 5 for movement in the direction of axis of the handle 1. The thruster 5 and the head 2 are coupled to each other through a toggle link 4. The thruster 5 is urged towards the head 2 by a force exerted by a spring 6. Balls 7 are incorporated so as to reduce friction between the side surfaces of the head 2 and the inner surfaces of the handle 1. Numeral 8 designates a roller which serves to reduce friction between the thruster 5 and the inner surface of the handle 1. Numeral 9 designates an adjusting screw for adjusting the resilient urging force of the spring 6, while numeral 10 denotes a grip secured to the end of the handle 1 opposite to the head 2.
In tightening a bolt or the like, when the tightening load in terms of torque reaches a predetermined level of torque, the toggle link 4 starts to operate so that the head 2 collides with an abutment portion 100 of the handle 1, accompanied by an impacting sound and an abrupt reduction in the torque which inform the user of the tightening of the bolt or the like with predetermined level of torque.
One of the shortcomings of these prior art torque wrench devices is as follows. The torque wrench device described above is a consolidated torque wrench having a toggle link incorporated therein. A head-interchangeable torque wrench device also has been known which can be used in combination with different types of wrenches such as a ratchet wrench, spanner wrench and ring spanner, as disclosed in, for example, Japanese Utility Model Publication No. 49-17509. This known head-interchangeable torque wrench device, however, requires that all the different types of wrenches are designed specifically so as to be adapted to the torque wrench device. In other words, the known head-interchangeable torque wrench device is not a universal torque wrench which can be used in combination with a variety of types of wrenches such as diversified designs of ratchet wrench, spanner wrench, ring spanner and so forth. Consequently, it has been necessary to prepare a variety of types of heads corresponding to a variety of type of wrenches.
In addition, known head-interchangeable wrench devices have been produced in different standards by different manufacturers, thus hampering interchangeability of the torque wrench devices. In addition, it is not easy for ordinary users to purchase individual wrenches of different types, which causes inconvenience to the users.
Another shortcoming of the known torque wrench device is as follows. In the known torque wrench device as described, the tightening torque (compression load) is adjusted by varying the compression load of the spring 6 through rotating the adjusting screw 9 provided on the end of the handle 1. This means that the tightening torque is adjustable only over a range which is limited by the elastic characteristic of the spring. Thus, the known torque wrench device is adaptable only to a limited range of tightening torque. In other words, it has been impossible to adjust the tightening torque over an extensive range.